Associations among soil microbial and plant richness across global terrestrial biomes

Abstract Soil microbiomes play a crucial role in terrestrial ecosystems by influencing plant diversity and ecosystem functions, yet global patterns linking soil microbial and plant species richness remain unclear. Here we employed machine learning models integrating environmental variables to map global richness patterns of plants, bacteria, and fungi across terrestrial biomes and examined their associations. We found distinct biogeographical distributions and high diversity regions: plant richness peaked in tropical forests, soil bacterial richness was highest towards arid and transitional zones, and soil fungal richness was prominent in tundra and boreal forests. Notably, plant richness correlated positively with microbial richness and strongly with fungal endophyte richness, supporting the concept that diversity fosters further diversity. These findings reveal complex cross-kingdom interactions shaping terrestrial biodiversity and underscore the importance of integrated conservation strategies that consider multiple organismal groups and their environmental drivers.